Regnerative burner

ABSTRACT

A regenerative burner or heat exchanger has a housing with a removable media bed, which can be removed from the housing for regeneration, replacement or other treatment of the media. A spare media bed can be prepared with new, renovated or otherwise treated media and ready to replace the bed in the heat exchanger with minimal delay. Another heat exchanger housing has a detachable lower section, containing heat exchange media, which can be moved for regeneration, replacement or other treatment of the media.

RELATED APPLICATION

[0001] This application claims the priority of provisional applicationserial No. 06/239,983, filed Oct. 16, 2000.

FIELD OF THE INVENTION

[0002] This inventions relates to regenerative burners, and moreparticularly to an improved method and apparatus for recovering exhaustfor use in preheating the air used for combustion in the burner.

BACKGROUND

[0003] Regenerative burners are used on furnaces to improve efficiencybecause they recover sensible heat that would otherwise be wasted.Generally a regenerative burner captures waste heat from the exhaustgasses that leave a furnace and uses the heat to preheat combustion air.The use waste heat to preheat combustion air improves the efficiency ofthe furnace or process in which the burner is used.

[0004] One common type of regenerative burner requires the use of a pairof burners in tandem. One burner is ignited at a time and while it isburning the exhaust gases from the furnace are routed through a heatexchange media associated with the second burner which captures heatfrom the furnace exhaust. The first burner is then extinguished and thesecond burner is ignited. Combustion air for the second burner is routedthrough the heated media and becomes preheated as it approaches theburner. The use of the preheated combustion air improves the efficiencyof the burner. While the second burner is burning, exhaust gasses fromthe furnace are routed through heat exchange media associated with thefirst burner. The process is then repeated, each burner using preheatedcombustion air. The timing of the switch from one burner to the other iscommonly controlled to maximize the efficiency of the furnace or processto which the burner is attached by recovering the maximum practicalamount of waste heat.

SUMMARY OF THE INVENTION

[0005] The present invention is an improvement in the design of aregenerative burner, to the method for its operation and, in particular,the design of the heat exchange media bed associated with the burner.One embodiment of the invention has a regenerative burner, or heatexchanger, with a housing containing a removable media bed. Heatexchange media is carried by the bed, and the bed can be removed fromthe housing, with the media, for regeneration, replacement or othertreatment of the media. Preferably, the heat exchanger has a spare mediabed that can be prepared with new, renovated or otherwise treated media,ready to replace the bed in the heat exchanger with minimal delay whenthe heat exchange media needs replacement, renovation or othertreatment.

[0006] In another embodiment, the heat exchanger housing has adetachable lower section. The lower section contains heat exchangemedia, and can be moved for regeneration, replacement or other treatmentof the media.

[0007] Other features and advantages of this invention will be apparentfrom the accompanying drawings and the following detailed description.

DRAWINGS

[0008]FIG. 1 is a cross-sectional view of a conventional regenerativeburner.

[0009]FIG. 2 Figure is a cross sectional side elevation view of aregenerative burner embodying the present invention.

[0010]FIG. 3 is cross sectional end elevation view of the regenerativeburner shown in FIG. 2.

[0011] FIGS. 4-9 provide plan, elevation and sectional views of aremovable cassette or bed for the regenerative heat exchanger shown inFIGS. 2 and 3.

[0012] FIGS. 10-13 provide elevation and sectional views of a secondembodiment of this invention.

DETAILED DESCRIPTION

[0013] The conventional regenerative burner shown in FIG. 1 has aburner, generally indicated as 1, and an associated heat exchanger,generally indicated as 2. This burner is used in tandem with anidentical or other similar burner. During operation one burner isignited and burned for a predetermined period of time. During this timeexhaust air from the furnace is routed through the heat exchange mediaof the second burner. The exhaust gases leave the furnace and enter theburner housing at 3 and pass down through pipe section 4, through heatexchange media 5 and out through port 6. From this point the exhaustgases are routed to auxiliary pollution control equipment (not shown) ordirectly to the atmosphere. More than one port may be provided, howeveronly one is required for operation. Additional ports may be connected toalternate exhaust gas pipes and controlled by valves or merely coveredor have optional apparatus such as vibratory cleaning devices attachedto them. Depending on the contents of the furnace a small amount ofmaterial from the furnace may become entrained in the stream of exhaustgases and be deposited in the heat exchange media bed. This material issolid, liquid or gaseous initially but all of the material deposited inthe heat exchange media will be either solid or liquid. Gases willcontinue through the heat exchange media with the exhaust stream. Aftera period of time that is typically less than a minute, the first burneris extinguished and the second burner is ignited. When this occurs thecombustion air for the second burner is routed so that it enters themedia bed associated with the second burner where it is preheated,passes into the burner housing and takes part in the combustion process.At the same time the exhaust from the furnace is routed out through thefirst burner in the same manner described above preheating the heatexchange media associated with the first burner.

[0014] The heat exchanger design shown in FIG. 1 is provided with twoaccess doors 8 and 9 to permit the periodic maintenance and cleaning ofthe heat exchange media. As mentioned above, material from the furnacemay be entrained in the exhaust gases and deposited on the media. Duringroutine maintenance, the heat exchanger is allowed to cool down and door9 is opened and the media is raked or shoveled from the heat exchanger.Conventional heat exchange media can be used. The media typicallycomprises ceramic balls of a single size or a mixture of various sizes.The media may be other shapes as well. The composition of the media canbe selected based on the environment to which it will be exposed.However, in all cases the media must be able to withstand hightemperatures and sudden thermal shocks. High alumina ceramic balls ofabout 1 inch in diameter are a convenient and effective material for useas heat exchange media.

[0015] After the media is removed from the heat exchanger bed it iscleansed by tumbling or scrubbing to remove the deposited materials.After cleaning the media may be reused if it is still in satisfactorycondition. It is not unusual for media to be reused many times dependingon the environment to which it is exposed. Door 9 is then closed andclean media is charged into the heat exchanger bed through door 8. Thenewly charged media should be leveled in the heat exchanger bed aftercharging to insure proper exhaust gas flow through the bed of media.

[0016] The above described routine cleaning and maintenance can requireseveral hours to complete and requires workers to perform many operationin close proximity to hot furnace surfaces.

[0017] The present invention comprises improvements to the design of theheat exchanger portion of a regenerative burner to permit easier andfaster maintenance and cleaning of the heat exchanger media.

[0018] The redesigned heat exchanger permits the media and thesupporting carrier, cassette or other bed in which it rests to beremoved from the heat exchanger housing as a unit. One embodiment of theimproved design is shown in FIGS. 2 and 3. FIG. 2 shows a side view of across section of a regenerative burner with a heat exchanger cassette,carrier or other bed modified in accordance with the present invention.FIG. 3 is an end view of a cross section of the regenerative burnershown in FIG. 2. The media bed is no longer an integral part of the heatexchanger housing, but has been redesigned as a removable cassette shownmore clearly in FIGS. 4-9. To maintain the heat exchanger with this newconfiguration, door 10 is opened and media bed 11 is removed as a unit.Because of the size of some of these units, a forklift or similar devicemay be required to remove the media bed 11, and rectangular tubes 12 areprovided to facilitate such removal. Tubes 12 are adapted to receive theforks of a forklift and provide a convenient mechanism for removal ofthe media bed. After removal, the media is dumped from the bed andreplaced with clean media. As with conventional regenerative burners,the media can be cleaned and reused. A forklift equipped with rotaryforks can be used to facilitate the dumping of the media bed.

[0019] In one embodiment of the invention, the media bed is tapered froma smaller end, designed to be inserted into the heat exchanger housingfirst, to a larger end as shown in FIGS. 5 and 9. This permits easyinsertion of the media bed into the heat exchanger housing and helpsinsure that a good seal is established around the media bed and thehousing so exhaust gas does not leak around the media and escape withoutpassing through the media bed. Gasket material may be placed around thetop of the media bed to help form a good seal with the heat exchangerhousing. Optionally, gasket material may be used at other locations asrequired or desirable. However, it is still desirable to have the mediain the bed filled to a uniform level to improve the performance of theheat exchanger. To achieve this uniform level with the tapered bedshown, rigid combustible boards can be placed along the inside of thevertical walls of the media bed to extend the effective height of themedia bed walls to a uniform level. Media can then be placed in the bedto a level approximately equal to the height of the combustible boardsand will retain the boards in place during insertion of the bed. Afterthe burners operate for a short period, the combustible boards will burnup and the media will settle slightly in the bed forming a level bedwell sealed to the heat exchanger housing. Media 7 filled to a uniformlevel in a tapered bed is illustrated in FIG. 2.

[0020] A further technique for obtaining a good seal between the mediabed and the heat exchanger housing is to precompress the gasket materialand retain it in the compressed state with adhesive tape while the mediabed is inserted into the heat exchanger housing. The tape can be anycommon paper, plastic film or cloth backed tape. After the burnersoperate for a short period, the tape will burn away and release thegasket material to expand and form a good seal.

[0021] The media bed shown in FIGS. 4-9 comprises a rectangular verticalfront wall 12, a rectangular back wall 13 and two tapered side walls 14.Each of the walls is lined with a refractory material 18 and terminatesat the bottom with a horizontal flange 15 that supports a perforatedgrate 16. The grate 16 both supports the media and permits the exhaustgasses to pass through. If equipped with optional forklift tubes 16, thetubes may have holes 17 to permit exhaust gasses to also pass throughthis portion of the media bed.

[0022] A second embodiment of the invention is shown in FIGS. 10-13. Inthis embodiment, the heat exchanger housing is split into two piecesalong a horizontal plane. The lower section contains the heat exchangermedia and is fastened to the upper section by detachable fasteners.Screw jacks 24 are illustrated for this purpose.

[0023] The regenerative burners shown in this embodiment also operate inpairs as described above. The exhaust passes out of the furnace throughpipe 19, down through media bed 20, along passage 21, up through passage22 and out through exhaust port 23.

[0024] During routine cleaning and maintenance, the lower section of theheat exchanger housing is detached from the upper section. Optionally,it may be convenient to support the lower section using a forklift. If aforklift is used, the forks are inserted in optional rectangular tubes24. The media is then dumped from the media bed located in the lowersection of the heat exchanger housing and replaced with clean media.After a uniform layer of clean media has been placed in the media bed,the lower section of the heat exchanger is reattached to the uppersection. Again, gasket material may be used to seal the joint betweenthe upper and lower sections.

[0025] The furnace down time required for the periodic cleaning andmaintenance of the media in the heat exchangers may be further reducedby the use of a spare media bed or lower section. In this case the sparecan be prepared and equipped with clean media and set aside until it isneeded. Then, when the cleaning and maintenance function is performed,the media bed may be removed as described above, and immediatelyreplaced with the prepared spare media bed. (Or, in the case of theregenerative burner shown in FIGS. 10-13, the lower section can beremoved and replace with a spare prepared lower section.) The burnerscan then be reignited. At some time between maintenance intervals, themedia bed, or lower section, as appropriate, can be dumped, refilledwith clean media and set aside until needed.

[0026] As those skilled in the art will readily appreciated, theembodiments described above proved dramatic improvements in regenerativeburners or heat exchangers, and their operations. The time required toreplace a removable, bed of heat exchange material is significantlyreduced, in comparison to current methods for treating regenerating orotherwise treating heat exchange material in burner or heat exchanger.In addition, hazards and inconvenience associated with current methodsare largely avoided.

[0027] Of course, those skilled in the art will also appreciate thatnumerous modifications can be mad to the equipment and methods definedabove within the scope of this invention, which is defined by thefollowing claims.

We claim:
 1. A regenerative heat exchanger system comprising a housing,a removable media bed within said housing, and heat exchange mediacarried by said bed, said bed being designed and adapted for removal ofsaid bed from said housing with said media for regeneration, replacementor other treatment of said media.
 2. A regenerative heat exchangersystem according to claim 1 wherein said media bed comprises a frontwall, a rear wall that is larger than said front wall, side walls thatare tapered from said front wall to said rear wall, and a perforatedgrate supported by said front, rear and side walls, said grate beingdesigned and adapted to hold said heat exchange media and to allowexhaust gas or intake air to contact said media.
 3. A regenerative heatexchanger system according to claim 1 wherein said bed further comprisesone or more tubes adapted to receive a fork of a forklift.
 4. Aregenerative heat exchanger system according to claim 1, furthercomprising a spare media bed that can be prepared with new, renovated orotherwise treated media and ready to replace the bed in said heatexchanger with minimal delay when the heat exchange media within saidheat exchanger needs replacement, renovation or other treatment.
 5. Aregenerative heat exchanger system according to claim 1, wherein saidhousing having an upper section and a detachable lower section, saidlower section containing heat exchange media and being adapted to bemoved from said upper section for regeneration, replacement or othertreatment of said media.
 6. A regenerative heat exchanger systemaccording to claim 5 wherein said bed further comprises one or moretubes adapted to receive a fork of a forklift.
 7. A regenerative heatexchanger system according to claim 1 wherein said media comprisesceramic particles.
 8. A regenerative heat exchanger system according toclaim 7 wherein said particles comprise balls having an average diameterof about 1 inch.
 9. In a furnace comprising: a first burner and a secondburner; a first regenerator and a second regenerator; exhaust ductingfrom said first burner to said first regenerator; exhaust ducting fromsaid second regenerator to said second regenerator; intake ducting fromsaid first regenerator to said second burner; intake ducting from saidsecond regenerator to said first burner; and means for alternately:passing intake air through said first regenerator to said second burnerand passing exhaust gas from said second burner through said secondregenerator; and passing intake air through said second regenerator tosaid first burner and passing exhaust gas from said first burner throughsaid second regenerator; the improvement wherein: said first regeneratorand said second regenerator each comprise a carrier for heat exchangemedia that is designed and adapted to be removed from said regeneratorsfor renovation of said media.
 10. A furnace according to claim 9,further comprising a spare carrier of heat exchange media that can berenovated and prepared for service while said furnace is in operation.11 In a heat recovery method wherein exhaust gas from one or moreburners is passed through one or more beds of regenerative material thatis heated by said exhaust gas, and intake air for said burners is passedthrough and heated by beds of said material, the improvement whereinsaid beds are placed on supports that can be removed for regeneration ofsaid material.